Mother of five Nargis Begum, 62, died on the M1 in South Yorkshire in September 2018 when another vehicle smashed into her car which she had just climbed out of to seek help.
At an inquest hearing, Doncaster coroner Nicola Mundy had said that Highways England could have to answer manslaughter charges in connection with her death.
But yesterday South Yorkshire Police said it was no longer pursuing a case of corporate manslaughter.
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Lawyers on behalf of Mrs Begum’s family and Claire Mercer, whose husband Jason, 47, was killed in a separate crash on the M1 near Sheffield, have said they are not prepared to let the matter drop.
Helen Smith, a specialist smart motorways lawyer at Irwin Mitchell, said: “Claire and Nargis’s family as well as many others continue to have serious concerns about smart motorways and their safety.
“We keep on hearing worrying first-hand stories of how people are being seriously injured or killed on smart motorways while the independent report we commissioned through road safety experts also highlighted grave concerns.
“While we thank the police and Crown Prosecution Service for their thorough investigation the families we represent are obviously disappointed by the decision. However, this doesn’t mean their quest for meaningful change is over.
“We’ll continue to support families and are determined to provide them with the answers they deserve through the civil courts.”
Yesterday, South Yorkshire Police Assistant Chief Constable Sarah Poolman said: "I would like to express my heartfelt sympathies to the families and loved ones of those who have lost their lives on the smart motorway in South Yorkshire.
"Families and campaigners are fighting with dignity and admirable determination in their search for answers and action following these tragedies.
"Following concerns expressed by senior coroner Nicola Mundy at the pre-inquest review into the death of Mrs Nargis Begum, the force launched a 'scoping exercise' to ascertain whether there is a reasonable suspicion that Highways England may have committed the criminal offence of corporate manslaughter.
"As part of our work, we sought specialist advice from the Crown Prosecution Service (CPS).
"Having considered the CPS advice, we have concluded that in the circumstances, Highways England cannot be held liable for the offence of corporate manslaughter.
"This is because, in legal terms, the organisation did not owe road users a 'relevant duty of care' under the terms set out in the Corporate Manslaughter and Corporate Homicide Act 2007.
"For this reason, I have brought the police investigation into this offence to an end.
"I regret that South Yorkshire Police is unable to provide all the answers that families and campaigners are looking for.
"However, I can assure them that a thorough and comprehensive report comprising our findings and all of the materials we have gathered during our scoping exercise is now being completed.
"This report will be provided to Ms Mundy before Mrs Begum's inquest is resumed. It can also be made available to the government and Highways England, with a view that its contents may help inform further enquiries into smart motorways via other avenues in the future."